Influence of the fluorine-oxygen substitution on the ionic conductivity properties of lithium tellurite glasses

A large range of glassy compositions has been found inside the ternary LiF-Li2O-TeO2 system. The influence of the fluorine-oxygen substitution on the ionic conduction properties of (50-x)LiO0.5-(x)LiF-(50)TeO2 ([MATH]) glasses has been investigated. These results have been correlated with the data relative to ion distribution and microstructure obtained by NMR and TEM. A maximum of conductivity associated with a minimum of activation energy is observed for [MATH]. The composition dependence of conductivity with rising x can be explained by a progressive decrease of the F-F associations around the Te4+ ions and a simultaneous increase of the Li-F associations. The clustering of the Li+ and F- ions produces small domains which hinder the Li+ ions diffusion in these glasses